Pressure-senstive adhesives and process for preparing them

ABSTRACT

The invention relates to a process for preparing a pressure-sensitive adhesive based on at least one polymer, in the course of which said at least one polymer is crosslinked, the polymer having functional groups Y and having been admixed, further, with at least one kind of functionalized particles which have at least one nonpolymeric base unit, wherein the particles having a surface modification of the base unit, the surface modification of the particles having at least one kind of functional groups X, and the crosslinking of the polymer being brought about at least in part by a reaction of the functional groups X of the particles and the functional groups Y of the polymer, and further to pressure-sensitive adhesives based on at least one crosslinked polymer component, the crosslinking of the polymer component being brought about at least in part by incorporation of the functionalized particles, the particles having at least one nonpolymeric base unit and also a surface modification of this base unit, and the surface modification of the particles having at least one kind of functional groups X which are capable of reacting with functional groups Y present in the polymer component, and also to the use of surface-modified functionalized particles having a nonpolymeric base unit as crosslinking reagents for crosslinking polymers for preparing pressure-sensitive adhesives.

This application is a Continuation of U.S. application Ser. No.11/233,456 filed Sep. 22, 2005, pending, which claims foreign prioritybenefit under 35 U.S.C. §119 of German Patent Application No. 10 2005022 782.1 filed May 12, 2005.

The present invention relates to pressure-sensitive adhesives whichpreferentially can be processed without solvent and are distinguishednot only by good processing properties and, in particular, coatabilitybut also by good product properties. The invention embraces thecomposition of innovative pressure-sensitive adhesive formulations andalso their preparation, processing, and use in self-adhesive products.Also part of this invention is an innovative scheme allowing thecombination of good processing properties and good product properties tobe realized for pressure-sensitive adhesive formulations of this kind.

BACKGROUND OF THE INVENTION

Within the field of adhesives, pressure-sensitive adhesives (PSAs) arenotable in particular for their permanent tack. A material which haspermanent tack must at any given point in time have an appropriatecombination of adhesive and cohesive properties. This distinguishes it,for example, from reactive adhesives, which in the unreacted state offervirtually no cohesion. For good product properties it is appropriate toadjust PSAs in such a way that the balance of adhesive and cohesiveproperties is at an optimum. This balance is typically achieved byconverting polymer chains present in PSA formulations into wide-meshednetworks. The nature of this network has a critical influence on theadhesive and cohesive properties of the PSA. A material featuringpronounced crosslinking, although having good cohesion, nevertheless hasreduced pliancy, so that the material is unable to adapt adequately tothe roughness of a substrate surface. Moreover, a material featuringpronounced crosslinking has only a relatively low ability to dissipatedeformation energy such as occurs under load. Both phenomena reduce thebond strength. A material with a low level of crosslinking, in contrast,although able to flow on rough surfaces and to dissipate deformationenergy, with the consequence that the adhesion requirements may be met,is nevertheless inadequate in its resistance to load, owing to a reducedcohesion.

One kind of crosslinking which has an effect on the adhesion/cohesionbalance is temporary polymer-chain interlooping. However, this issufficient for adequate cohesion of the PSA only when the molar mass ofthe polymers is sufficiently high. PSAs based on natural rubbers mayrest solely on this crosslinking principle. Further possibilities ofsetting the crosslinking of the PSA are chemical crosslinks, which aretherefore irreversible. Chemical crosslinking can also be achieved bymeans of radiation treatment of the PSAs. Another possibility is toutilize physical crosslinking principles. Examples of such crosslinks,typically thermoreversible, in PSAs are present in thermoplasticelastomers, such as in certain block copolymers or semicrystallinepolymers.

Besides the crosslinking principles referred to, it is also possible touse fillers for raising the cohesion. In that case a combination offiller/filler interactions and filler/polymer interactions frequentlyleads to the desired reinforcement of the polymer matrix. A raising ofcohesion based thereon represents a further physical crosslinkingvariety.

For fillers which are mentioned with a view to a reinforcing effect inPSAs, the class of the pyrogenic (or fumed) silicas deserves particularmention. These silicas are used, inter alia, as thickeners, gellingagents or thixotropic agents in a very wide variety of fluids, utilizingtheir effect on the rheological properties of the fluids. The use ofhydrophilic and of hydrophobic silica is described in this context.Examples of the use of pyrogenic silica in the field of PSAs aredescribed in U.S. Pat. No. 4,163,081 by Dow Corning, in U.S. Pat. No.4,710,536 by 3M and in DE 102 08 843 A1 by BASF AG.

As further fillers, the use of modified phyllosilicates for improvingproduct properties has been described in WO 02/81586 A1 by 3M, in WO02/24756 A2 by Rohm & Haas and in JP 2002 167,557 by Sekisui.

In all of these cases the reinforcement results from the effect of theparticles on the elasticity modulus of the elastomer composite. Theinteraction in this case is brought about by physical interactionsbetween individual particles, on the one hand, and between particles andpolymers, on the other. Often, however, these physical interactions arenot enough to withstand even low mechanical deformations, such as mayoccur, for example, when a PSA joint is loaded by shearing or peeling.This nonlinear phenomenon is known as the Payne effect and is manifestedas a loss of elasticity modulus under deformation. A review of thedescription of this effect and of various approaches as a mechanisticexplanation is given by Heinrich and Klüppel [G. Heinrich, M. Klüppel,Adv. Polym. Sci., 2002, 160, 1-44].

In the preceding section, a variety of examples have been given of typesof crosslinking that may be employed in PSAs for improving the productproperties, especially the cohesion. For each of these varieties ofcrosslinking, the question arises of to what extent they affect theprocessing properties, and more particularly the coatingcharacteristics. This is debated below.

Besides the product properties and hence the optimum balance of adhesiveand cohesive properties in a PSA, its processing properties are also ofcentral importance. Generally speaking, the processing properties of aformulation are reduced by its crosslinking. In a majority of casesindeed, processing becomes impossible. It is therefore advantageous tocarry out or to initiate crosslinking not until during or afterprocessing, and in particular during or after coating. However, wherethe crosslinking state results from the mere presence of a constituentin the formulation, as is the case with the abovementioned fillers, thenthe processing characteristics are adversely affected by its verypresence. Polymers with high molar masses are likewise among formulationconstituents which by virtue of their state of interlooping haveadvantageous product properties and yet, likewise owing to their stateof interlooping, may show disadvantages in processing properties. Inboth cases, namely both interlooping and fillers, the physicalprinciples which lead to the crosslinking of the PSA system and hence toadvantageous product properties have negative consequences for theprocessing characteristics, particularly the coatability.

Traditional approaches to escaping this dilemma have been based on theuse of solvents as operating assistants. An increased environmentalawareness and the desire for evermore efficient production techniques,however, are underlying the trend toward solvent-free operations. Incomparison to solvent processing methods, the polymer-based PSA basecompositions, in the case of the hotmelt processes have a state ofcrosslinking in their melt, as a result of the interlooping and/orfiller particles, which is associated with significantly higherviscosities and elasticities.

In contrast to physical modes of crosslinking, chemical crosslinkingmethods afford the formation of a network which can be initiated by anappropriate operating regime only during processing. However, the use ofchemical crosslinkers is limited by their pot-life reactivity. If thenetwork forms in too pronounced a way before the material has beencoated, the elasticity increase which has already taken place results ina deterioration in the processing properties, and reduced-qualitycoating outcomes may result. One particular difficulty arises in thecase of solvent-free systems, since, here, elevated temperatures arenecessary for processing, leading at the same time to an acceleration ofthe chemical crosslinking reaction.

One example of a system of this kind is described in U.S. Pat. No.4,524,104 by Sanyo. Radiation crosslinking methods appear advantageousin this context, since only after coating is the formation of a networkinitiated deliberately, as proposed for example in EP 377 199 by BASF.However, in order to obtain networks having a structure satisfying thesubsequent product requirements in respect of shear strength, polymersof decidedly high molar mass are needed, which in turn, as a result oftheir state of interlooping, may have disadvantages in terms ofprocessing characteristics.

Typically, the processing properties of a material deteriorate as itselasticity goes up. Formation of a network always leads to an increasein the storage modulus and hence to upper elasticity. Consequently,there is a deterioration in the fluidity, which is needed for processingof the coating, or even a complete loss of fluidity. In the case ofcoating, then, inhomogeneities may occur in the coating outcome,possibly going as far as melt fracture. A variety of authors describethis phenomena, especially for capillary dies and extrusion dies.Literature references on this can be found in Pahl et al. [M. Pahl, W.Gleiβle, H.-M. Laun, Praktische Rheologie der Kunststoffe andElastomere, 4th ed., 1995, VDI Verlag, Düsseldorf, p. 191f] and Tanner[R. I. Tanner, Engineering Rheology, 2nd ed., 2000, Oxford UniversityPress, Oxford, p. 523f].

Systems are therefore sought which preferably can be coated withoutsolvent and which exhibit a combination of good product properties onthe one hand—and here particularly in respect of cohesion—and improvedprocessing properties on the other, especially coatability.

One particularly advantageous example of systems which at least partlysatisfy this combination of requirements is represented by blockcopolymers comprising segments which soften at high temperatures (knownas the hard phase) and others which at application temperature arepresent in melted form. The softening temperature of the hard phase istypically adjusted, through the use of specific monomers, such that goodproduct properties prevail at room temperature and yet at temperaturesthat are rational from an operational standpoint the material can easilybe coated from the melt. Since these materials typically do not havehigh molar masses, their melt viscosity and elasticity, as soon as thehard phase is in softened form, are comparatively low.

A disadvantage of the above-discussed PSAs based on block copolymers,however, is their thermal shear strength, which is limited by thesoftening of the hard domains that sets in at an elevated temperature. Afurther disadvantage to be cited are the costly and inconvenientpreparation conditions for block copolymers. In order to be able toprepare polymers having the requisite block like structure in sufficientquality, controlled or living polymerization techniques are necessary,some of which are complex. Moreover, not all monomer combinations canalways be easily realized. Hence the block copolymer approach, on theone hand, therefore, is seen as not being universally flexible fornumerous polymer systems. On the other hand there is a need for PSAshaving better thermal shear strength.

It is therefore an objective of the present invention to provide aflexible scheme which encompasses a suitable combination of material andprocess so that it is possible to prepare PSAs which can preferably beprocessed without solvent and which have good processing properties andgood product properties.

SUMMARY OF THE INVENTION

As has now been found, this combination of requirements, consisting ofgood processing properties and good product properties, can be obtainedby preparing crosslinked PSAs using a process in which a specific PSAformulation comprises particles functionalized in such a way that,during or after the coating operation, the particles can be linked to atleast one kind of polymeric constituents of the PSA formulation byexposure to radiation energy, in particular to electromagneticradiation, to particulate radiation and/or to thermal energy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the overall process of the invention.

FIG. 2 illustrates the formation of a bond between functional groups Xand Y.

FIG. 3 shows two examples of the coupling of reactive constituents viaformation of hydrogen bonds and via direct coupling of polymer A toparticle B using a coupling reagent.

FIG. 4 illustrates the coupling of polymer A and filler B through metalof type M.

FIG. 5 illustrates coupling of polymer A and filler B through acceptorand donor groups.

FIG. 6 illustrates the construction of self-adhesive products of theinvention.

DETAILED DESCRIPTION

The present invention relates to a process for preparing a crosslinkedpressure-sensitive adhesive, to crosslinked pressure-sensitive adhesivesobtainable by such a process, and to the use of such adhesives. Theinvention further embraces intermediates from such a process,particularly the composition of innovative formulations forpressure-sensitive adhesives. The combination of the innovative PSAformulations of the invention with the preparation process of theinvention is likewise inventive and a central component of thisspecification (in this regard cf. also FIG. 1).

The invention relates to a process for preparing a pressure-sensitiveadhesive based on at least one polymer A, in the course of which said atleast one polymer A is crosslinked, the polymer having functional groupsY and having been admixed, further, with at least one kind offunctionalized particles B (also called “filler particles” below). Theparticles have at least one nonpolymeric base unit and also a surfacemodification of this base unit, the surface modification of the baseunit having at least one kind of functional groups X. In accordance withthe invention the crosslinking of the polymer is brought about at leastin part by a reaction of the functional groups X of the particles andthe functional groups Y of the polymer. Within the sense of theinvention the crosslinking may also be brought about completely by meansof the functionalized particles.

The dependent claims relate to advantageous versions of the process ofthe invention.

The invention further provides a pressure-sensitive adhesive based on atleast one crosslinked polymer component A, the crosslinking of thepolymer component A being brought about at least in part byincorporation of functionalized particles B, the particles B having atleast one nonpolymeric base unit and also a surface modification of thisbase unit, and the surface modification of the particles B having atleast one kind of functional groups X which are capable of reacting withfunctional groups Y present in the polymer component A.

A pressure-sensitive adhesive of this kind is to be presented as beingin accordance with the invention particularly if it is obtainable by theprocesses described as being in accordance with the invention.

The invention additionally provides for the use of surface-modifiedparticles having a nonpolymeric base unit, particularly of particles ofthe kind described in the context of this specification, as crosslinkingreagents of polymers for preparing pressure-sensitive adhesives.

Also considered as being in accordance with the invention are thepolymers A which have as yet not been crosslinked but have been admixedwith the functionalized particles B. In the pressure-sensitive adhesiveto be crosslinked there may be further components present.

The PSA formulations of the invention comprise at least one kind of apolymer A which contains at least one kind of groups of type Y, and alsoat least one kind of filler particles B containing on their surface atleast one kind of groups of type X. Groups of type Y and of type X havebeen selected for the purposes of this invention such that exposure toelectromagnetic radiation, particulate radiation and/or thermal energyforms a bond between at least one group of type Y and at least onefunctional group of type X, thereby producing an adduct of typeB—X′—Y′-A (see FIG. 2). The designation X′ here denotes that thestructure of the functional group X may have altered following reaction.Similarly, the designation Y′ indicates that the structure of thefunctional group Y may have altered following reaction. It is likewisein accordance with the invention for the functional groups X and Y notto have altered in their structure and yet still to have entered into alinkage.

In this description the terms “electromagnetic radiation” and“particulate radiation” are to be understood to mean all forms ofradiation, a summary having been given by V. D. McGinniss [V. D.McGinniss in Encyclopedia of Polymer Science and Engineering, H. F.Mark, N. M. Bikales, C. G. Overberger, G. Menges (eds.), 2nd ed., 1986,Wiley, New York, vol. 4, p. 418ff]. These radiation forms can beemployed with preference in accordance with the invention.

Through the inventive use of the innovative formulations described here,in combination with the process described here, advantageouslycrosslinked PSAs are obtained. The functionalized filler particles B actas polyfunctional crosslinkers. As a result of their capacity to linktwo or more polymer chains in one crosslinking point it is possible toreduce the molar mass of the polymeric constituents of the PSA that areto be crosslinked (on the basis of polymeric constituents for the PSAwhich—in relation to customary, prior-art processes—have a reduced molarmass). There follows an improvement in the processing characteristics.Conversely, within the context of this invention, it is also possible toadmix the filler particles of the invention to PSAs which comprisecrosslinkable polymers of low molar mass. Following exposure toelectromagnetic radiation, particulate radiation and/or thermal energy,different network structures are obtained than if the filler particlesof the invention had not been present. A feature of this innovativestate of crosslinking is that it correlates with improved productproperties, particularly an increased cohesion of the PSA. Typically itis characteristic of the innovative state of crosslinking that theadhesive properties of the PSAs of the invention are at least at thelevel also occupied by a crosslinked PSA which contains no inventivefiller particles but has been processed in a comparable way and has acomparable gel fraction.

An advantageous approach is for the PSA formulations of the invention,comprising at least one kind of an inventive polymer A and at least onekind of a functionalized filler particle B, to have good processingproperties in the raw state—that is, before processing commences. Byprocessing properties for the purposes of this invention are meant inparticular the viscosity of the PSA formulation and also its elasticity.The viscosity is reported as zero-shear viscosity η₀ for differenttemperatures. It can be obtained from viscosity curves determined bycapillary viscosymmetry. The elasticity is reported in the form of thefirst normal stress difference N₁, again at different temperatures. Thedata for the first normal stress difference, too, can be obtained fromcapillary viscosymmetry experiments. Both variables, the viscosity andthe first normal stress difference, are generally dependent on shearrates for PSA formulations. Depending on process and the shear rateswhich occur therein, therefore, they may vary for a given PSAformulation. For the description of this invention it is sensible tolimit oneself to one shear rate; however, this does not restrict in thisrespect the processes which can be used in accordance with theinvention. As one such shear rate the shear rate of 1000 s⁻¹ is selectedas a representative, advantageous value. For the processing propertiesand particularly the coatability it is very advantageous not to exceed adefined ratio of elasticity and viscosity at the shear rate dictated bythe process. If this ratio is too high, the elastic character of thematerial to be coated is predominant. A consequence of that can be meltfracture, which is manifested in a non-homogeneous coating pattern (M.Pahl, W. Gleiβle, H.-M. Laun, Praktische Rheologie der Kunststoffe undElastomere, 4th ed., 1995, VDI Verlag, Düsseldorf, p. 191f).

In accordance with information gained from capillary-viscosimetricrheology, the ratio R=N₁/τ of first normal stress difference N₁ andshear stress τ determines the processing characteristics of a polymermelt [W. Gleiβle, Rheol. Acta, 1982, 21, 484-487; M. Pahl, W. Gleiβle,H.-M. Laun, Praktische Rheologie der Kunststoffe und Elastomere, 4thed., 1995, VDI Verlag, Düsseldorf, p. 320ff]. The shear stress τ is theproduct of viscosity and shear rate. The numerator of the ratio N₁/τhence describes the elastic properties of the material, the denominatorthe viscous properties. The latter, moreover, illustrates the dependenceon the operating speed in the form of the shear rate. Above a criticalrate for R, flow anomalies occur. If, therefore, at the shear rateswhich prevail during processing, success is achieved in reducing N₁ by adesign of material, or at least in not causing it to grow further as aresult of additional crosslinking effects, the expectation is then thatthe material will be able to be coated without melt inhomogeneities.This can be accomplished, for example, by not initiating crosslinkinguntil after coating, such as is possible, for example, in the case ofradiation treatment. The irradiated and thus crosslinked material has anincreased elasticity and, in association with this, a higher firstnormal stress difference, and in this state could not be processed witha good coating pattern. The uncrosslinked melt, however, is lesselastic, exhibits a lower first normal stress difference, and can becoated successfully. For PSAs with good cohesion there is frequently aneed for polymers having high molar masses. These polymers, however, mayhave high elasticities even in the chemically uncrosslinked state, owingto intermolecular interactions, such as interlooping, and this may leadto disadvantages in the coating characteristics.

The innovative concept of the invention encompasses accomplishing thecohesion of the PSA of the invention essentially by means of an improvedstate of crosslinking via chemical linking of polymers to fillersurfaces. A high polymer molar mass is therefore no longer mandatoryand, consequently, the coating characteristics are not so pronouncedlyrestricted as a result of chain interlooping. The particles themselves,during processing, are in the form of a disperse phase in the PSAformulation. Since at this time they have not yet undergone chemicallinkage with polymeric constituents of the formulation, at this timetheir contribution to the elasticity of the formulation is incomplete.Only when the crosslinking reaction is initiated, during and/or aftercoating, is the desired cohesion produced. The requirements imposed onthe PSA formulations of the invention are therefore that the formulationin the uncrosslinked state should exhibit good processing properties,provided for example by a low first normal stress difference, and inparticular the ratio R, and in the crosslinked state should exhibit goodcohesion, provided for example by the holding power or the gel fractionof a self-adhesive tape test specimen.

Advantageous PSAs of the invention, obtained by way of the inventivecoating and crosslinking operation, typically have a holding poweraccording to test D that is at least 50% higher, preferably at least100% higher, than that of a formulation coated and crosslinked inexactly the same way but containing no filler particles of the inventionand yet having a comparable gel fraction (test B). The adhesion, givenby the bond strength according to test C, of the PSA system of theinvention is typically at least at the same level occupied by that ofthe aforementioned reference system, or preferably is in fact at least25% higher. At the same time, the R value of the inventive PSA in theuncrosslinked state, at a temperature which is appropriate in a way thatis specific to the particular material, of between 25° C. and 300° C.,exhibits virtually no increase, likewise in comparison to a formulationthat contains no filler particles of the invention and is alsouncrosslinked, and remains at values of preferably not more than R=3.5(test A2). The viscosity of the PSAs of the invention at the sametemperature is no higher or only slightly higher, specifically not morethan, preferably, 25% higher, than that of a formulation that containsno filler particles of the invention and is also uncrosslinked (testA1).

Composition of Inventive PSA Formulations

The PSA formulations of the invention comprise at least one kind ofpolymer, A, and at least one kind of filler particle, B, the at leastone polymer kind A being able, via groups Y present in it, to join withgroups X, located on the surface of the at least one filler particlekind B, through exposure to electromagnetic radiation, particulateradiation and/or thermal energy during and/or after a coating operation.The PSA of the invention may optionally comprise further constituents inaddition to polymers A and filler particles B. This section will addressthe polymers A of the invention, the fillers B of the invention, andfurther constituents which may be used optionally in the PSAformulations of the invention, and will also describe the nature of thegroups X and Y.

The PSAs of the invention contain advantageously up to 50% by weight ofat least one filler particle kind B, preferably up to 20% by weight,very preferably up to 12% by weight.

Polymers A

The at least one polymer kind A is preferably in accordance with theinvention when it has a molar mass of not more than 10 000 000 g/mol,preferably not more than 500 000 g/mol. Furthermore, the at least onepolymer kind A preferably has a softening temperature of less than 100°C., more preferably less than 20° C. The at least one polymer kind A maybe of linear, branched, star-shaped or grafted structure, to give but afew examples, and may be in the form of a homopolymer or randomcopolymer. The term “random copolymer” encompasses for the purposes ofthis invention not only copolymers in which the comonomers used for thepolymerization have been incorporated in purely random fashion but alsothose in which there are gradients in the comonomer composition and/orlocal accumulations of individual comonomer kinds in the polymer chains.

The molar mass is to be understood in this context as referring to theweight average of the molar mass distribution, as is obtainable, forexample, via gel permeation chromatography analyses. By softeningtemperature in this context is meant the glass transition temperaturefor amorphous systems and the melting temperature for semicrystallinesystems, and may be determined, for example, by dynamic differentialcalorimetry (DSC). Where numerical values are given for softeningtemperatures, they relate in the case of amorphous systems to themiddle-point temperature of the glass stage and in the case ofsemicrystalline systems to the temperature at maximum heat evolutionduring the phase transition.

Within the sense of this invention it is possible, moreover, for the atleast one polymer kind A to be a block copolymer. Of particularadvantage are block copolymers in which, preferably, each of the blockspresent (independently of one another) has a molar mass of less than 1000 000 g/mol, preferably less than 250 000 g/mol, is of linear,branched, star-shaped or grafted structure and/or is in the form of ahomopolymer or random copolymer. With further advantage at least onekind of block has a softening temperature of less than 100° C.,preferably less than 20° C. The individual kinds of block occurring inthe block copolymer may differ with regard to the comonomer compositionand optionally may differ in their molar mass and/or softeningtemperature and/or structure (e.g., linear or branched identity). Thedifferent polymer arms in star-shaped and grafted systems may bechemically different in nature: that is, may be composed of differentmonomers and/or may have a different comonomer composition.

Polymers of kind A are also preferred in accordance with the inventionwhen they contain at least one kind of groups Y which are able to enterinto a bond, during or after a coating operation, with groups X presenton the surface of the at least one filler particle kind B, on exposureto electromagnetic radiation, particulate radiation and/or thermalenergy. The groups of the at least one kind Y may be present in adiversity of ways in the at least one polymer kind A. The at least onepolymer kind A may be constructed, for example, as a homopolymer frommonomers which contain the at least one kind of groups Y. Furthermore,the at least one polymer kind A may also be constructed as a randomcopolymer which is obtained at least from one kind of monomers whichcontain the at least one kind of groups Y and, optionally, from one ormore kinds of monomers which contain no such groups. A furtherpossibility is for the at least one polymer kind A to contain the atleast one kind of groups Y only at certain points along the polymerbackbone. Examples of such embodiments include groups which are locatedat chain ends, in the region of chain points or blocking-agent points,in the region of branching points or in the region of block connectionpoints. Polymers of the at least one kind A are particularly preferredin accordance with the invention when the polymer molecule contains onaverage at least two such groups. It is possible, furthermore, for theat least two groups Y to be introduced into the at least one polymer Aby way of a grafting reaction. It is likewise in accordance with theinvention to introduce the at least two groups Y into the at least onepolymer kind A by carrying out a polymer-analogous reaction.Furthermore, any desired combinations of the stated modes offunctionalization are in accordance with the invention.

As examples of polymers A, but without wishing to impose anyrestriction, mention may be made of the following homopolymers andrandom copolymers as being advantageous for the purposes of thisinvention: polyethers, such as polyethylene glycol, polypropylene glycolor polytetrahydrofuran, polydienes, such as polybutadiene orpolyisoprene, hydrogenated polydienes, such as polyethylene-butylene orpolyethylene-propylene, rubbers, such as natural rubber, nitrile rubberor chloroprene rubber, butadiene rubber, isoprene rubber, andpolyisobutylene, polyolefins, such as ethylene homopolymers orcopolymers, propylene homopolymers or copolymers, metallocene-catalyzedpolyolefins, polysiloxanes, polyalkyl vinyl ethers, polymers ofunfunctionalized α,β-unsaturated esters, copolymers based onα,β-unsaturated esters, copolymers based on alkyl vinyl ethers, and alsoethylene-vinylacetate copolymers, EPDM rubbers, and styrene-butadienerubbers. Further random copolymers which can be used with advantage areobtained by copolymerizing isoprene and/or butadiene, feature 1,4, 1,2and/or 3,4, or 1,4 and/or 1,2, incorporation of the monomers into thepolymer chain, and may be in fully or partly hydrogenated form.

Copolymers which can be used with particular advantage for the purposesof this invention are random copolymers based on unfunctionalizedα,β-unsaturated ethers. When they are used for the at least one polymerkind A with copolymer character, then monomers which can be used fortheir preparation are, advantageously, in principle all compoundsfamiliar to the skilled worker that are suitable for polymer synthesis.Preference is given to using α,β-unsaturated alkyl esters of the generalstructure

CH₂═CH(R¹)(COOR²)  (I)

where R¹═H or CH₃ and R²═H or represents linear, branched or cyclic,saturated or unsaturated alkyl radicals having 1 to 30, in particularhaving 4 to 18, carbon atoms.

Monomers which can be used with great preference in the sense of generalstructure I for polymers A with copolymer character include acrylic andmethacrylic esters with alkyl groups consisting of 4 to 18 carbon atoms.Specific examples of such compounds, without wishing to be restricted bythis enumeration, include n-butyl acrylate, n-butyl methacrylate,n-pentyl acrylate, n-pentyl methacrylate, n-hexyl acrylate, n-hexylmethacrylate, n-heptyl acrylate, n-heptyl methacrylate, n-octylacrylate, n-octyl methacrylate, n-nonyl acrylate, n-nonyl methacrylate,n-decyl acrylate, n-decyl methacrylate, dodecyl acrylate, dodecylmethacrylate, hexadecyl acrylate, hexadecyl methacrylate, octadecylacrylate, octadecyl methacrylate, their branched isomers, such assec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate,tert-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexylmethacrylate, and isooctyl acrylate, and also cyclic monomers such as,for example, cyclohexyl acrylate, cyclohexyl methacrylate, norbornylacrylate, norbornyl methacrylate, isobornyl acrylate and isobornylmethacrylate.

Likewise possible for use as monomers for polymers A with copolymercharacter are acrylic and methacrylic esters which contain aromaticradicals, such as phenyl acrylate, benzyl acrylate, benzoin acrylate,phenyl methacrylate, benzyl methacrylate or benzoin methacrylate.

A further possibility for use in accordance with the invention areethoxylated and propoxylated acrylates and methacrylates. In systems ofthis kind the acrylate or methacrylate side chains are composed formallyof an oligomer or polymer or ethylene oxide or of propylene oxide.

It is additionally possible, optionally, to use vinyl monomers from thefollowing groups: vinyl esters, vinyl ethers, vinyl halides, vinylidenehalides, and also vinyl compounds containing aromatic rings andheterocycles in a position. For the vinyl monomers which can be employedoptionally, mention may be made by way of example of selected monomerswhich can be used in accordance with the invention: vinyl acetate,vinylformamide, vinylpyridine, ethyl vinyl ether, 2-ethylhexyl vinylether, butyl vinyl ether, vinyl chloride, vinylidene chloride,acrylonitrile, styrene, and α-methylstyrene.

In one preferred version of this invention the at least one polymer kindA contains its at least two groups Y in the form of at least onespecific comonomer which has been randomly copolymerized during thepolymerization of the polymer. The molar fraction (chemical amountfraction) of this at least one specific comonomer in relation to thecomposition of the total monomer mixture during the preparation of thetotal polymer is up to 50% by weight, preferably up to 20% by weight,very preferably up to 5% by weight. The specific character of this atleast one comonomer is expressed in the fact that it carries at leastone group Y which is able to enter into a bond, during or after acoating operation, with at least one group X, located on the surface ofthe at least one filler particle kind B, on exposure to electromagneticradiation, particulate radiation and/or thermal energy. Examples ofgroups X and Y are described in the section “Combinations of groups Xand Y”. Particular preference is given to using monomers based onα,β-unsaturated esters which contain these groups. It is also possiblefor groups Y to be joined by way of a polymer-analogous reaction withthe polymer A at the sites at which these specific comonomers have beenincorporated. A further possibility is for these specific comonomers tobe derivatized with groups Y prior to polymerization; in other words,for comonomers with functionalization which is not necessarily inaccordance with the invention to be modified, prior to polymerizationand hence preparation of a polymer kind of type A, with a chemicalassembly via which the at least one inventive group Y is incorporatedinto the comonomer and, following this modification reaction andsubsequent polymerization, is available for the forming of a linkage, inaccordance with the invention, with at least one group X.

As examples of comonomers which carry functional groups, mention may bemade—without wishing to impose any restriction—of allyl acrylate, allylmethacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfurylmethacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutylacrylate, 4-hydroxybutyl methacrylate, glycidyl acrylate, glycidylmethacrylate, acrylated benzophenone, methacrylated benzophenone,crotonic acid, maleic acid, maleic anhydride, itaconic acid, itaconicanhydride, 2-dimethylaminoethyl acrylate, 2-dimethylaminoethylmethacrylate, 3-dimethylaminopropyl acrylate, 3-dimethylaminopropylmethacrylate, N-tert-butylacrylamide, N-tert-butylmethacrylamide,N-isopropylacrylamide, N-isopropylmethacrylamide, acrylamide,methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, acrylicacid, methacrylic acid, vinyl alcohol, 2-hydroxyethyl vinyl ether,3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether and allylglycidyl ether.

If the at least one polymer kind A is a block copolymer then in thesimplest case the copolymers present are diblock copolymers of the formPA-PA′, composed of a block PA and a block PA′, which differ in respectof the starting monomers selected and may optionally be different intheir softening temperature and/or molar mass and/or structure (e.g.,linear or branched). Further embodiments of polymers A with blockcopolymer character, without wishing to impose any restriction, aretriblock copolymers of the type PA-PA′-PA″, block copolymers of the typePA-PA′-PA″-PA′, and higher block copolymers whose structures continuethis series. Triblock copolymers and higher block copolymers are inaccordance with the invention, in the sense of polymers A with blockcopolymer character, when all blocks linked directly to one another aredifferent in respect of the selected starting monomers and also,optionally, in their molar mass and/or softening temperature and/orstructure (e.g., linear or branched). Further, triblock copolymers andhigher block copolymers are in accordance with the invention, in thesense of polymers A, if two or more of the blocks which are not linkeddirectly to one another are not different from one another in respect ofthe selected starting monomers and also, optionally, in their molar massand/or softening temperature and/or structure (e.g., linear orbranched). A preferred version of a polymer A with block copolymercharacter is a triblock copolymer of the type PA-PA′-PA″, where PA andPA″ are identical in respect of the selected starting monomers, molarmass, softening temperature, and structure. The block linkage inpolymers A with block copolymer character may take a linear form oralternatively a star-shaped embodiment, or a graft copolymer variant.Each individual block may be constructed as a homopolymer block orcopolymer block. The blocks are therefore subject to the samedefinitions as given in the section “Homopolymers” and “Randomcopolymers”.

Where a block copolymer is employed as polymer A, then preferably atleast one kind of block contains functionalizations of type Y.Particular preference is given to diblock copolymers which containfunctionalizations of type Y in only one kind of block; symmetricaltriblock copolymers which contain functionalizations of type Y only intwo end blocks; and triblock copolymers which contain functionalities oftype Y only in the middle block.

Filler Particles B

As the at least one filler particle kind B for the purposes of thisinvention use is made preferably of filler particles in which the baseunits without surface modifications have softening temperatures ofgreater than 200° C., preferably of greater than 500° C. Furthermore,systems of the kind whose softening temperature (based on the unmodifiedbase units) is above the decomposition temperature are in accordancewith the invention when the decomposition temperature is above 200° C.,preferably above 500° C.

The materials on which the base unit of the at least one filler particlekind B is based may be inorganic in nature or may be anorganic/inorganic hybrid material and may have an amorphous, partlycrystalline or crystalline character. Base units of organic nature canalso be used for the purposes of the invention.

In terms of their structure, the filler particles may be presentpreferably in spherical form, rodlet form or platelet form. Separateparticles, often also called primary particles, are in accordance withthe invention just as much as aggregates formed from a plurality ofprimary particles. Such systems often exhibit a fractal superstructure.Where the particles are formed from crystallites, the primary particleform depends on the nature of the crystal lattice. Platelet-form systemscan also be present in the form of layer stacks.

In one advantageous embodiment of this invention the at least onefunctionalized filler kind is present in the pressure-sensitive adhesivesubstantially in the form of singular spherical particles. In that casethe particle diameters have values of less than 500 nm, preferably ofless than 100 nm, very preferably of less than 25 nm. In a furtheradvantageous version of this invention the at least one functionalizedfiller kind is present in the pressure-sensitive adhesive substantiallyin the form of singular platelet-shaped particles. The layer thicknessof such platelets then has values of preferably less than 10 nm and agreatest diameter of preferably less than 1000 nm. In a furtheradvantageous version of this invention the at least one filler kind ispresent in the pressure-sensitive adhesive substantially in the form ofsingular rodlet-shaped particles. In this case these rodlets have adiameter of less than 100 nm and a length of less than 15 μm. Therodlets may also be curved and/or flexible. Furthermore, it is possiblewith advantage for the purposes of this invention for the at least onefiller kind to be present in the pressure-sensitive adhesive in the formof primary particle aggregates. These aggregates have a gyration radius(to be understood in analogy to the term “radius of gyration” as knownfrom polymers) of less than 1000 nm, preferably of less than 250 nm.Particular preference is given for the purposes of this invention tousing filler particles of the kind whose spatial extent in at least onedirection is less than 250 nm, preferably less than 100 nm, verypreferably less than 50 nm. It is possible for the purposes of thisinvention, furthermore, to use combinations of the aforementioned typesof filler.

Typical classes of compound, advantageous in accordance with theinvention, of which the base unit of the at least one filler particlekind B is composed are oxides of inorganic nature—particularly metaloxides and/or semimetal oxides—salts of alkaline earth metals, andsilicate-based minerals, especially clay minerals and clays. Theamorphous or crystalline metal oxides that can be used in accordancewith the invention include, for example, silicon dioxide, aluminumoxide, titanium dioxide, zirconium dioxide, and zinc oxide. The skilledworker is familiar with further systems, which may likewise be used inaccordance with the invention. Alkaline earth metal salts include, forexample, carbonates, sulfates, hydroxides, phosphates, and hydrogenphosphates of magnesium, of calcium, of strontium, and of barium. Theclay minerals and clays which can be used in accordance with theinvention include, in particular, silicatic systems such as serpentines,kaolins, talc, pyrophyllite, smectites such as particularlymontmorillonite, vermiculites, illites, mica, brittle mica, chlorites,sepiolite, and palygorskite. Additionally it is possible to usesynthetic clay minerals such as hectorites and also systems relatedthereto, such as Laponite® from Laporte, and fluorohectorites andsystems related thereto, such as Somasif® from Co-Op, in accordance withthe invention.

The at least one filler particle kind B is in a surface-modified form.Surface modification reagents that are typical and advantageous inaccordance with the invention are organosilanes and surfactants, butalso organotitanium compounds, fatty acids or polyelectrolytes such as,for example, short-chain polymers having a high acrylic acid fraction.The primary function of these surface modification reagents is to createcompatibility between the particle surface and the matrix into which theparticles are to be dispersed. As a further function, surfacemodification reagents are used in order to prevent relatively smallparticles coming together to form larger objects. It is veryadvantageous for the purposes of the invention to use at least one kindof surface modification reagent which in addition to the compatibilizingand aggregation-preventing function also affords the possibility ofentering, via at least one group X incorporated in the at least one kindof surface modification reagent, into a connection with at least onegroup Y, present in at least one polymer kind A, on exposure toelectromagnetic radiation, particulate radiation and/or thermal energy,during or after a coating operation. A filler particle carries on itssurface preferably at least 10 groups of the at least one kind X, morepreferably at least 50.

Filler particles which in their natural form (in the form of the baseunit without surface modification) contain hydroxide groups on thesurface afford the possibility, preferably, of a reaction withchlorosilanes or alkoxysilanes. Hydrolysis of the silane is followed bycondensation of silanol groups with the hydroxide groups on the particlesurface. If at least one substituent on the central silicon atom of thesilane is an organic radical, then in the case of complete surfacecoverage with silane molecules an organophilic casing is linkedcovalently in this way to the filler particle, and hence the particlesare made compatible with the polymer matrix. The concepts and typicallyused classes of material which can be employed for the purposes of thisinvention are described, for example by R. N. Rothon [R. N. Rothon(ed.), “Particulate-Filled Polymer Composites” 2nd ed., 2003, RapraTechnology, Shawbury, 153-206].

Two classes of silanes can be distinguished in particular for thepurposes of this invention: on the one hand, those which, in addition tothe groups capable of reaction with the base surface, carry exclusivelyorganic radicals which are chemically inert (see structure II); on theother, those which, in addition to the groups capable of reaction withthe base surface, contain at least one organic radical which carries atleast one group X that is able to enter into a bond with at least onegroup Y present in at least one polymer kind A on exposure toelectromagnetic radiation, particulate radiation and/or thermal energy,during or after a coating operation (see structure III). In silane II atleast one of substituents A, B, and D is a hydrolyzable group, i.e., achlorine atom or an alkoxy group, for example. At least one ofsubstituents B, C, and D is an organic radical which is composed of alinear, branched or cyclic hydrocarbon, which may also be aromatic andis of low molecular mass or oligomeric or polymeric in nature. If thereis more than one hydrolyzable group among substituents A, B, and D, thenthe groups involved may be chemically identical or different, or meetingthe above definition of hydrolyzable groups. If there is more than oneorganic radical among substituents B, C, and D, then these radicals maylikewise be chemically identical or different, or meeting the abovedefinition of organic radicals. In silane III at least one ofsubstituents A, E, and F is a hydrolyzable group, i.e., a chlorine atomor an alkoxy group, for example. At least one of substituents E, F, andG is an organic radical which is composed of a linear, branched orcyclic hydrocarbon, which may also be aromatic and is of low molecularmass or oligomeric or polymeric in nature and which additionallycontains at least one group X which is able, during or after a coatingoperation, to enter into a bond with at least one group Y present in atleast one polymer kind A on exposure to electromagnetic radiation,particulate radiation and/or thermal energy. If there is more than onehydrolyzable group among substituents A, E, and F, then the groupsinvolved may be chemically identical or different. If there is more thanone organic radical among substituents E, F, and G, then the radicalsinvolved may likewise be chemically identical or different, or meetingthe above definition of organic radicals.

Advantageous embodiments of silanes of structure II that are useful inaccordance with the invention are those in which only A is employed as ahydrolyzable group and B, C, and D are organic radicals, of which B andD are chemically identical and C is chemically different. Furtheradvantageous embodiments of silanes of structure II that are useful inaccordance with the invention are those in which A and B are employed aschemically identical hydrolyzable groups and C and D are chemicallyidentical organic radicals. Further advantageous embodiments of silanesof structure II that are useful in accordance with the invention arethose in which A, B, and D are employed as chemically identicalhydrolyzable groups and C is an organic radical.

Advantageous embodiments of silanes of structure III that are useful inaccordance with the invention are those in which only A is employed as ahydrolyzable group and E, F, and G are organic radicals, of which E andF are chemically identical and G is chemically different. G contains theat least one group X which, during or after a coating operation, is ableto enter into a bond with at least one group Y present in at least onepolymer kind A on exposure to electromagnetic radiation, particulateradiation and/or thermal energy. Further advantageous embodiments ofsilanes of structure III that are useful in accordance with theinvention are those in which A, E, and F are employed as chemicallyidentical hydrolyzable groups and G is an organic radical which containsthe at least one group X which, during or after a coating operation, isable to enter into a bond with at least one group Y present in at leastone polymer kind A on exposure to electromagnetic radiation, particulateradiation and/or thermal energy.

Hydrolyzable groups A, B, D, E, and F which may be employed withadvantage in silanes II and silanes III are halogen atoms, especiallychlorine, and/or alkoxy groups, such as methoxy, ethoxy, n-propoxy,isopropoxy, n-butoxy, sec-butoxy or tert-butoxy groups. Acetoxy groupsare a further possibility for use. The additional examples ofhydrolyzable groups, known to the skilled worker, may likewise beemployed for the purposes of this invention.

The organic radicals B, C, D, E, and F which may be employed in silanesII and silanes III include by way of example, with no claim tocompleteness, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl,and tert-butyl groups, pentyl groups and also the branched isomers,hexyl groups and also the branched isomers, heptyl groups and also thebranched isomers, octyl groups and also the branched isomers, nonylgroups and also the branched isomers, decyl groups and also the branchedisomers, undecyl groups and also the branched isomers, dodecyl groupsand also the branched isomers, tetradecyl groups and also the branchedisomers, hexadecyl groups and also the branched isomers, octadecylgroups and also the branched isomers, and eicosyl groups and also thebranched isomers. The organic radicals of the invention may,furthermore, contain cyclic and/or aromatic moieties. Representativestructures are cyclohexyl, phenyl, and benzyl groups. It is further inaccordance with the invention if as at least one organic radical use ismade of oligomers or polymers which contain at least one hydrolyzablesilyl group.

The organic radicals E, F, and G in which there is at least one group Xwhich, during or after a coating operation, is able to enter into a bondwith at least one group Y present in at least one polymer kind A onexposure to electromagnetic radiation, particulate radiation and/orthermal energy include, for example, the compounds compiled in thefollowing list (the list makes no claim to completeness): methyl, ethyl,n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups, pentylgroups and also the branched isomers, hexyl groups and also the branchedisomers, heptyl groups and also the branched isomers, octyl groups andalso the branched isomers, nonyl groups and also the branched isomers,decyl groups and also the branched isomers, undecyl groups and also thebranched isomers, dodecyl groups and also the branched isomers,tetradecyl groups and also the branched isomers, hexadecyl groups andalso the branched isomers, octadecyl groups and also the branchedisomers, and eicosyl groups and also the branched isomers. The organicradicals of the invention may, furthermore, contain cyclic and/oraromatic moieties. Representative structures are cyclohexyl, phenyl, andbenzyl groups. It is further in accordance with the invention if as atleast one organic radical use is made of oligomers or polymers whichcontain at least one hydrolyzable silyl group. Where a radical from theabove list is employed as one or more of radicals E, F, and G, it isadditionally modified by a chemical moiety which contains at least onegroup X.

Examples of silanes of structure II that can be used with preference forthe purposes of this invention are methyltrimethoxysilane,methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane,trimethylethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane,propyltriethoxysilane, isobutyltrimethoxysilane,isobutyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane,isooctyltrimethoxysilane isooctyltriethoxysilane,hexadecyltrimethoxysilane, hexadecyltriethoxysilane,octadecylmethyldimethoxysilane, phenyltrimethoxysilane,phenyltriethoxysilane, cyclohexylmethyldimethoxysilane, anddicyclo-pentyldimethoxysilane.

An example of silyl-functionalized oligomers or polymers which can beemployed in accordance with the invention is polyethylene glycol whichhas been linked with a trimethoxysilane group.

Representatives of silanes of structure III which can be used withparticular preference for the purposes of this invention and which carryat least one functionalization are, for example,N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,N-(2-aminoethyl)-3-amino-propyltriethoxysilane,3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,3-aminopropyldiethoxymethylsilane,N-(2-aminoethyl)-3-aminopropyldimethoxymethylsilane,(N-butyl)-3-aminopropyltrimethoxysilane,3-(N-ethylamino)-2-methylpropyltrimethoxysilane,4-amino-3,3-dimethylbutyltrimethoxysilane,4-amino-3,3-dimethylbutyldimethoxymethylsilane,(N-cyclohexyl)aminomethyldimethoxymethylsilane, (N-cyclohexyl)aminomethyltrimethoxysilane, (N-phenyl)-3-aminopropyltrimethoxysilane,(N-phenyl)amino-methyldimethoxymethylsilane,(N-benzyl-2-aminoethyl)-3-aminopropyltrimethoxysilane[2-(N-benzyl-N-vinylamino)ethyl]-3-aminopropyltrimethoxysilane hydrogenchloride,[2-(N-benzyl-N-vinylamino)ethyl]-3-aminopropyltrimethoxysilane,bis(3-propyltriethoxysilyl)amine, vinyltrimethoxysilane,vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane,vinyltriisopropoxysilane, vinyldimethoxymethylsilane,vinyltriacetoxysilane, 3-triethoxysilylpropylsuccinic anhydride,3-glycidyloxypropyltrimethoxysilane,3-glycidyloxy-propyltriethoxysilane,2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,3-glycidyloxy-propyldiethoxymethylsilane,3-methacryloyloxypropyltrimethoxysilane,3-methacryloyloxypropyltriethoxysilane,3-methacryloyloxypropyltriisopropoxysilane,3-methacryloyloxypropyldimethoxymethylsilane,3-methacryloyloxypropyldiethoxymethylsilane,3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane,3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane,isocyanatomethyltrimethoxysilane, isocyanatomethyldimethoxymethylsilane,tris[3-(trimethoxysilyl)propyl] isocyanurate,3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane,2-hydroxy-4-(3-triethoxysilylpropoxy)benzophenone,4-(3′-chlorodimethylsilylpropoxy)benzophenone,3-mercaptopropyltrimethoxysilane, 3-mercaptopropyldimethoxymethylsilane,bis(3-triethoxysilylpropyl)disulfane,bis(3-triethoxysilylpropyl)tetrasulfane,bis(triethoxysilylpropyl)polysulfane, andoctadecylaminodimethyltrimethoxysilylpropylammonium chloride.

Silanes which are disclosed in WO 00/43539 by Biochip Technologies or inEP 281 941 B1 by Ciba Geigy, and those published by Kolar et al. [A.Kolar, H. F. Gruber, G. Greber, JMS Pure Appl. Chem., 1994, A31,305-318], may likewise be employed for the purposes of this invention assilanes of structure III. It is also possible to use organic titaniumcompounds, optionally in conjunction with silanes.

It is likewise of advantage in accordance with the invention to usesilanes of structure III which have been derivatized with a chemicalassembly which contains at least one group X. By this is meant thatsilanes of structure III with non inventive functionalization aremodified, before and/or after the surface modification reaction with thefiller particles, with a chemical assembly which introduces the at leastone inventive group X into the silane and after this silane modificationreaction and the surface modification reaction is available to form abond with at least one group Y.

The surface modification may take place completely by means of at leastone representative of the silanes III. It is also possible, though, touse a combination of silanes III and silanes II.

Such a combination is inventive if at least 1% by weight, preferably atleast 5% by weight, of at least one representative of the silanes III isused.

Silanes are used with particular preference for the purposes of thisinvention as surface modifiers if filler particles are employed which,at least in the state of the non-surface-modified base unit, carryhydroxyl groups on the surface. Examples of this kind of fillerparticles are metal oxides, especially amorphous silicon dioxide. Anexemplary possibility of realizing a surface modification is given byBauer and coworkers (F. Bauer, H. Ernst, U. Decker, M. Findeisen, H.-J.Gläsel, H. Langguth, E. Hartmann, R. Mehnert, C. Peuker, Macromol. Chem.Phys., 2000, 201, 2654-2659] and Rothon [R. N. Rothon (ed.), ParticulateFilled Polymer Composites, 2nd ed., 2003, Rapra Technology, Shawbury,pp. 153-206].

Particles which in the state of the non-surface-modified base unit carryionic groups on the surface can be modified preferably using surfactantsand/or fatty acids.

As surfactants it is possible in general to employ all quaternaryammonium compounds, protonated amines, organic phosphonium ions, andamino carboxylic acids that exhibit amphiphilic behavior. Advantageoususe may be made of ammonium compounds which carry at least three organicradicals, such as alkylammonium salts, trimethylalkylammonium salts,dimethyldialkylammonium salts, methylbenzyldialkylammonium salts,dimethylbenzylalkylammonium salts or alkylpyridinium salts. Furthermore,alkoxylated quaternary ammonium compounds may be employed.

Two classes of surfactants may be distinguished for the purposes of thisinvention: on the one hand, those which, in addition to the groupscapable of interaction with the base surface, carry exclusively organicradicals which are chemically inert (see structure IV); on the other,those which, in addition to the groups capable of linking with the basesurface, contain at least one organic radical which carries at least onegroup X which, during or after a coating operation, is able to enterinto a bond with at least one group Y present in at least one polymerkind A on exposure to electromagnetic radiation, particulate radiationand/or thermal energy (see structure V). In surfactant IV thesubstituents A, B, and D may independently of one another be organicradicals or hydrogen; the substituent C is a long-chain organic radical.Any anions can be employed as counterions. Examples are chloride,bromide, hydrogen sulfate, dihydrogen phosphate, and tetrafluoroborate.The skilled worker is aware of others which may likewise be employed forthe purposes of this invention. Independently of one another, theorganic radicals may be linear or branched, saturated or unsaturated,may be composed of aliphatic, olefinic and/or aromatic elements, and maycontain 1 to 22 carbon atoms. Typical substituents used as organicradicals include methyl groups, ethyl groups, n-propyl groups, isopropylgroups, n-butyl groups, sec-butyl groups, tert-butyl groups, linear orbranched pentyl groups, linear or branched hexyl groups, linear orbranched heptyl groups, linear or branched octyl groups, benzyl groups,or groups with higher numbers of carbon atoms. Long-chain organicradicals employed include, preferably, dodecyl groups, tetradecylgroups, hexadecyl groups, octadecyl groups or eicosyl groups insaturated or unsaturated form. Since the starting materials forsurfactant manufacture are frequently natural products, alkylsubstituents with only one length of chain are rarely encountered.Instead there is frequently a mixture of alkyl chains different inlength. Particularly preferred long-chain organic radicals used aretallow radicals (unsaturated) or hydrogenated tallow radicals(saturated). It is also in accordance with the invention for thesurfactant function to be taken on by oligomers or polymers which havebeen functionalized such that they carry at least one cationic group.

Examples which may be used with preference for the purposes of thisinvention as surfactants of structure IV are hexadecyltrimethylammoniumchloride or bromide, methylditallowylammonium chloride or bromide, inwhich the tallow radicals (“tallowyl”) may be saturated or unsaturated,dimethyltallowylbenzylammonium chloride or bromide, in which thetallowyl radicals may be saturated or unsaturated,dimethyltallowyl(2-ethylhexyl)ammonium chloride or bromide, in which thetallowyl radicals may be saturated or unsaturated, anddimethylditallowylammonium chloride or bromide, in which the tallowylradicals may be saturated or unsaturated.

Surfactants which are disclosed in EP 900 260 B1 by Akzo Nobel, U.S.Pat. No. 5,739,087 by Southern Clay, U.S. Pat. No. 5,718,841 by Rheox,U.S. Pat. No. 4,141,841 by Procter & Gamble, and by H Groβmann [H.Groβmann in Katalysatoren, Tenside and Mineralöladditive, H. Falbe, U.Hasserodt (ed.), 1978. G. Thieme, Stuttgart, p. 135ff] may likewise beemployed for the purposes of this invention as surfactants of structureIV.

Advantageous embodiments of surfactants of structure V that are usefulin accordance with the invention are those in which the substituents E,F, and G independently of one another may be organic radicals orhydrogen and the substituent C is a long-chain organic radical. Anyanions can be employed as counterions. Examples are chloride, bromide,hydrogen sulfate, dihydrogen phosphate, and tetrafluoroborate.Independently of one another, the organic radicals may be linear orbranched, saturated or unsaturated, may be composed of aliphatic,olefinic and/or aromatic elements, and may contain 1 to 22 carbon atoms.Typical substituents used as organic radicals include methyl groups,ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups,sec-butyl groups, tert-butyl groups, linear or branched pentyl groups,linear or branched hexyl groups, linear or branched heptyl groups,linear or branched octyl groups, benzyl groups, or groups with highernumbers of carbon atoms. Long-chain organic radicals employed include,preferably, dodecyl groups, tetradecyl groups, hexadecyl groups,octadecyl groups or eicosyl groups in saturated or unsaturated form.With regard to the starting materials for manufacturing surfactant V aswell, natural products are frequently employed, so that rarely are alkylsubstituents of a single chain length present; instead, a mixture ofalkyl chains of different lengths is present. Particularly preferredlong-chain organic radicals used are tallow radicals (unsaturated) orhydrogenated tallow radicals (saturated). It is also in accordance withthe invention for the surfactant function to be taken on by oligomers orpolymers which have been functionalized such that they carry at leastone cationic group. With regard to the surfactants V at least one ofsubstituents E, F, G, and C contains at least one group X which, duringor after a coating operation, is able to enter into a bond with at leastone group Y present in at least one polymer kind A on exposure toelectromagnetic radiation, particulate radiation and/or thermal energy.Surfactants disclosed in EP 900 260 B1 by Akzo Nobel, U.S. Pat. No.5,739,087 by Southern Clay, U.S. Pat. No. 5,718,841 by Rheox, U.S. Pat.No. 4,141,841 by Procter & Gamble, and by H Groβmann [H. Groβmann inKatalysatoren, Tenside and Mineralöladditive, H. Falbe, U. Hasserodt(ed.), 1978. G. Thieme, Stuttgart, p. 135ff] may likewise be employedfor the purposes of this invention as surfactants of structure V,provided they have been modified with at least one group X, in addition,under certain circumstances, to the structure disclosed.

Examples which can be employed with preference for the purposes of thisinvention as surfactants of structure V aremethyltallowyldi(2-hydroxyethyl)ammonium chloride or bromide,allyldimethyltetradecyl chloride or bromide,allyldimethylhexadecylammonium chloride or bromide, andallyldimethyloctadecylammonium chloride or bromide.

For the purposes of this invention it is possible with preference to usea combination of surfactants IV and surfactants V. In this embodiment ofthe invention, representatives of surfactants V are present at a levelof at least 1% by weight, preferably at least 5% by weight, among all ofthe surfactants employed. Furthermore, it is possible to use surfactantsIV or V in combination with cationic compounds which, though notthemselves surfactants, carry at least one group X which is able, duringor after a coating operation, to enter into a bond with at least onegroup Y present in at least one polymer kind A on exposure toelectromagnetic radiation, particulate radiation and/or thermal energy.At least 1% by weight, preferably at least 5% by weight, of a cationiccompound of this kind is used in accordance with the invention incombination with surfactants IV and/or V. Where cationic compounds ofthis kind are employed, the sum of surfactants IV and V employed is notmore than 99% by weight, preferably not more than 95% by weight, itbeing possible for surfactants V to be replaced entirely by surfactantsIV. Examples of such cationic compounds are(2-acryloyloxyethyl)(4-benzoylbenzyl)dimethylammonium chloride orbromide, 3-trimethyl-ammoniopropylmethacrylamide chloride or bromide,2-trimethylammmonioethyl methacrylate chloride or bromide,3-dimethylalkylammoniopropylmethacrylamide chloride or bromide, and2-dimethylalkylammoniomethyl methacrylate chloride or bromide.

Surfactants are used with particular preference for the purposes of thisinvention if the filler particles employed have negative charges orpartial charges on the surface (in the state of the non-surface-modifiedbase unit). Examples of this kind of filler particles are certain clayminerals, particularly smectites, in which intercalated cations may bereplaced by surfactants. One principle whereby such replacement may takeplace has been formulated by Lagaly [G. Lagaly in Tonminerale and Tone,K. Jasmund, G. Lagaly (ed.), 1993, Steinkopff, Darmstadt, p. 366ff].

It is possible, furthermore, to use combinations of inventive silanesand inventive surfactants. At least one of the surface modificationreagents employed contains at least one group X which, during or after acoating operation, is able to enter into a bond with at least one groupY present in the polymer kind A on exposure to electromagneticradiation, particulate radiation and/or thermal energy.

Further Constituents

It is additionally in accordance with the invention to use, optionally,polymers C containing at least one group of type X, and/or polymers Ccontaining at least one group X and at least one group of type Y, and/orpolymers C containing neither type-X nor type-Y groups. The compositionof those polymers, employable optionally, that contain no groups of typeX or Y are subject to the same details in terms of construction,composition, choice of monomers, softening temperature, and structure ascontained in the definition of the polymers A, apart from the detailsgiven there in respect of groups Y. Optionally employable polymerscontaining at least one group X are subject to the details given forpolymers A, but such polymers C contain groups of kind X and not groupsof kind Y and can therefore, during or after a coating operation, enterinto a bond with at least one group Y of the at least one polymer ofkind A by exposure to electromagnetic radiation, particulate radiationand/or thermal energy. The incorporation of groups X into polymers C issubject to the same details given for groups Y in the polymers A. Wherepolymers are employed that carry groups X and Y, then the same details,in terms of construction, composition, choice of monomers, softeningtemperature, and structure, apply as contained in the definition of thepolymers A, but with the addition that there is also at least one groupX present in the polymer. For the incorporation of groups X and Y intopolymers C which carry both kinds of groups, the details which apply arethe same as those given for the groups Y in the polymers A.

As further constituents the PSA formulations of the invention maycomprise tackifier resins, plasticizers, rheological additives,catalysts, initiators, stabilizers, compatibilizers, coupling reagents,crosslinkers, antioxidants, other aging inhibitors, light stabilizers,flame retardants, pigments, dyes, further fillers, especially those notincluded in at least one filler particle kind B, and/or expandants.

Combinations of Groups X and Y

The PSAs of the invention comprise at least one polymer kind A and atleast one filler particle kind B. Polymers A contain at least two groupsY; filler particles B contain at least one kind of groups X. Groups Xand Y are chosen for the purposes of this invention such that betweenthese groups X and Y or by way of these groups X and Y it is possible tobring about coupling between polymers A and filler particles B. Thecoupling is initiated during or after the coating operation by exposureto electromagnetic radiation, particulate radiation and/or thermalenergy. The coupling involves at least one group X and at least onegroup Y. By coupling of at least one group X and at least one group Y ismeant for the purposes of this invention, in particular

-   -   a chemical reaction in which the at least one group X reacts        with the at least one group Y and leads to the formation of a        covalent bond,    -   the formation of hydrogen bonds between the at least one group X        and the at least one group Y, and/or the formation of a        coordinative bond as a result, for example, of formation of a        complex, involving the at least one group X and the at least one        group Y, so that at least one donor/acceptor bond is formed.

The coupling in this case may take place between the groups X and Ydirectly or else by mediation through one or more further substances,such as coupling reagents or crosslinkers. The position and number ofgroups X and Y in the polymers A and filler particles B that can be usedin accordance with the invention are subject to the same definitionsgiven for the polymers A and the filler particles B.

Where the coupling of the invention between the at least one polymerkind A and the at least one filler particle kind B is to proceed via thegroups Y and X as a chemical reaction, the groups X and Y involved aredefined in particular in accordance with the following remarks.

The PSAs of the invention comprise at least one constituent whichcomprises at least one kind of inventive segments having the generalstructure (R^(o)R^(oo)R^(ooo)C)—X. R^(o), R^(oo) and R^(ooo) mayindependently of one another be saturated or unsaturated, aliphatic oraromatic hydrocarbon radicals which may also be linked to one anotherand may be identical or different. For the purposes of this invention itis also possible for the carbon atom in (R^(o)R^(oo)R^(ooo)C)—X itselfto be unsaturated. In that case said carbon atom is linked only to X andto one or two of the radicals R^(o), R^(oo) or R^(ooo). The radicalsR^(o), R^(oo), and R^(ooo) may independently of one another include anynumber of heteroatoms. The radicals R^(o), R^(oo), and R^(ooo) may be oflow molecular mass or may be polymeric in nature. Up to two of theradicals R^(o), R^(oo), and R^(ooo) may also be hydrogen atoms,moreover. At least one of the radicals R^(o), R^(oo), and R^(ooo) islinked by a chemical or ionic bond, by chemisorption or physisorption,to a filler particle of kind B. The group needed for the couplingreaction is designated X.

The at least one inventive segment of structure (R^(o)R^(oo)R^(ooo)C)—Xcan be reacted with at least one segment which is present in at leastone further constituent of the PSA of the invention and which has thegeneral structure (R*R**R***C)—Y. R*, R** and R*** may independently ofone another be saturated or unsaturated, aliphatic or aromatichydrocarbon radicals which may also be linked to one another and may beidentical or different. For the purposes of this invention it is alsopossible for the carbon atom in (R*R**R***C)—Y itself to be unsaturated.In that case said carbon atom is linked only to Y and to one or two ofthe radicals R*, R** or R***. The radicals R*, R**, and R*** mayindependently of one another include any number of heteroatoms. Theradicals R*, R**, and R*** may be of low molecular mass or may bepolymeric in nature. Up to two of the radicals R*, R**, and R*** mayalso be hydrogen atoms, moreover. At least one of the radicals R*, R**,and R*** is linked by a chemical bond, to a polymer chain of kind A. Thegroup needed for the coupling reaction is designated Y. In specificversions of this invention, single or plural radicals R*, R** or R***may be of the same identity as R^(o), R^(oo) or R^(ooo). It is also inaccordance with the invention if group X and group Y are identical. Inthis specific case the coupling takes place advantageously by means of acoupling reagent or by the action of a catalyst or initiator. For thepurposes of this invention it is particularly advantageous if thecoupling reaction is initiated by exposure to electromagnetic radiationand/or particulate radiation.

For the purposes of this invention it is possible to use an arbitrarilylarge number of further groups, which may react with a group X and/orwith a group Y.

A coupling reaction may proceed by chemical reaction directly betweenthe groups X and Y, so forming a species(R^(o)R^(oo)R^(ooo)C)—X′—Y′—(CR*R**R***) (see FIG. 2). In the case of achemical reaction, X′ and Y′ are the reaction products of the groups Xand Y respectively. In specific cases the coupling of groups X and Yrequires a coupling reagent X^(a)—Y^(a) or X^(a)—R^(a)—Y^(a). X^(a) andY^(a) are groups capable of reaction with groups X and Y, respectively,and may be identical or different. It is also possible, furthermore, tolink two groups X via coupling reagent Y—R^(b)—Y and also two groups Yvia a coupling reagent X—R^(b)—X. R^(a) and R^(b) can be saturated orunsaturated, aliphatic or aromatic hydrocarbon radicals and may containan arbitrary number of heteroatoms. The radicals R^(a) and R^(b) may beof low molecular mass or may be polymeric in nature.

Table 1 lists a number of examples of X and Y which can be used inaccordance with the invention. Combinations of groups which can be usedwith advantage are marked with a cross. In certain circumstances,additional reagents and/or special conditions are needed for thereaction between the groups indicated. Reagents of this kind are thenadded to the PSA formulation (see “Further constituents” section).Specific conditions such as temperature or radiation also come withinthe intention of this invention. The table does not make any claim tocompleteness, but is intended merely to indicate examples of groupswhich can be employed for the purposes of this invention, andcombinations of groups that can be employed. Further groups andcombinations, known to the skilled worker, for corresponding reactionsmay likewise be employed in accordance with the invention. The radicalsR¹, R², R³, R⁴, R⁵, and R⁶ and also R^(a), R^(b), R^(c), R^(d), R^(e)and R^(f) in Table 1 may independently of one another be saturated orunsaturated, aliphatic or aromatic hydrocarbon radicals, which maycontain any number of heteroatoms and may be of low molecular mass ormay be polymeric in nature, and/or, alternatively, may be hydrogenatoms. In accordance with the definition above, the radicals may beidentical or different in construction. The radicals R¹, R², and R³ maybe linked to one another, the radicals R⁵ and R⁶ may be linked to oneanother, the radicals R^(a), R^(b), and R^(c) may be linked to oneanother, and the radicals R^(e) and R^(f) may be linked to one another.Cyclic acid anhydrides such as maleic anhydride or succinic anhydridemay be attached arbitrarily as a chemical group to polymers A or fillerparticles B. Maleic anhydride offers the possibility, furthermore, ofbeing incorporated as a comonomer in polymers A.

The entry “-PI” in Table 1 refers to a group which is possessed of aphotoinitiator function. Irradiation with UV light of appropriatewavelength activates the group and, depending on the nature of thephotoinitiator, a free-radical reaction or a cationic reaction isinitiated. Suitable representatives of such groups are type-Iphotoinitiators, in other words α-cleaving initiators such as benzoinderivatives and acetophenone derivatives, benzil ketals or acylphosphineoxides, type-II photoinitiators, in other words hydrogen abstractorssuch as benzophenone derivatives and certain quinones, diketones andthioxanthones, and cationic photoinitiators, such as “photoacidgenerators” such as arylated sulfonium or iodonium salts and dimerizedarylated imidazole derivatives. Further, triazine derivatives can beused to initiate free-radical and cationic reactions.

Photoinitiating groups X and/or Y of type I include for the purposes ofthis invention, preferably, benzoin, benzoin ethers such as, forexample, benzoin methyl ether, benzoin isopropyl ether, benzoin butylether, benzoin isobutyl ether, methylolbenzoin derivatives such asmethylolbenzoin propyl ether, 4-benzoyl-1,3-dioxolane and itsderivatives, benzil ketal derivatives such as2,2-dimethoxy-2-phenylacetophenone or 2-benzol-2-phenyl-1,3-dioxolane,α,α-dialkoxyacetophenones such as α,α-dimethoxyacetophenone andα,α-diethoxyactophenone, α-hydroxyalkyl phenones such as1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanoneand 2-hydroxy-2-methyl-1-(4-isopropylphenyl)propanone,4-(2-hydroxyethoxy)phenyl-2-hydroxy-2-methyl-2-propanone and itsderivatives, α-aminoalkylphenones such as2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-2-one and2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one,acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphineoxide and ethyl-2,4,6-trimethylbenzoylphenylphosphinate, andO-acyl-α-oximino ketones.

Photoinitiating groups of type II that can be used with preference inaccordance with the invention are based for example on benzophenone andits derivatives such as 2,4,6-trimethylbenzophenone or4,4′-bis(dimethylamino)benzophenone, thioxanthone and its derivativessuch as 2-isopropylthioxanthone and 2,4-diethylthioxanthone, xanthoneand its derivatives, and anthraquinone and its derivatives.

Type-II photoinitiators are used with particular advantage incombination with nitrogen-containing coinitiators, known as aminesynergists. For the purposes of this invention it is preferred to usetertiary amines. Furthermore, in combination with type-IIphotoinitiators, hydrogen atom donors are employed advantageously.Examples thereof are substrates which contain amino groups. Examples ofamine synergists are methyldiethanolamine, triethanolamine, ethyl4-(dimethylamino)benzoate, 2-n-butoxyethyl 4-(dimethylamino)-benzoate,isoacryloyl 4-(dimethylamino)benzoate, 2-(dimethylaminophenyl)ethanone,and also unsaturated tertiary amines copolymerizable therewith,(meth)acrylated amines, unsaturated, amine-modified oligomers andpolymers based on polyester or polyether, and amine-modified(meth)acrylates. For the purposes of this invention it is possible forsuch chemical assemblies to be linked to polymers and/or fillers.

For the purposes of this invention it is also possible to use anydesired combinations of different varieties of type-I and/or type-IIphotoinitiating groups.

In one particularly preferred version of this invention, groups ofphotoinitiating character are present as groups Y in at least one kindof polymers A.

In a further particularly preferred version of this invention, groups ofphotoinitiating character are present as groups X in at least one kindof functionalized filler particles B.

When the coupling of the invention between the at least one polymer kindA and the at least one filler particle kind B proceeds via the groups Yand X by way of the formation of hydrogen bonds, the groups X and Yinvolved are defined in accordance with the following remarks. In thisregard see, for example, D. Philp, J. F. Stoddard, Angew. Chem., 1996,108, 1242-1286 or C. Schmuck, W. Wienand, Angew. Chem., 2001, 113,4493-4499.

The PSAs of the invention comprise in this case at least one constituentwhich comprises one kind of segments having the general structure(R^(#)R^(##)R^(###)C)—X^(#). R^(#), R^(##) and R^(###) may independentlyof one another be saturated or unsaturated, aliphatic or aromatichydrocarbon radicals which may also be linked to one another and may beidentical or different. For the purposes of this invention it is alsopossible for the carbon atom in (R^(#)R^(##)R^(###)C)—X^(#) itself to beunsaturated. In that case said carbon atom is linked only to X^(#) andto one or two of the radicals R^(#), R^(##) or R^(###). The radicalsR^(#), R^(##), and R^(#) may independently of one another include anynumber of heteroatoms. The radicals R^(#), R^(##), and R^(###) may be oflow molecular mass or may be polymeric in nature. Up to two of theradicals R^(#), R^(##), and R^(###) may also be hydrogen atoms,moreover. At least one of the radicals R^(#), R^(##), and R^(###) islinked by a chemical or ionic bond, by chemisorption or physisorption,to a filler particle of kind B. The group needed for the couplingreaction is designated X^(#).

The at least one inventive segment of structure(R^(#)R^(##)R^(###)C)—X^(#) is able to form hydrogen bonds with at leastone functional segment which is present in at least one furtherconstituent and which has the general structure(R^(˜)R^(˜˜)R^(˜˜˜)C)—Y^(˜). R^(˜), R^(˜˜) and R^(˜˜˜) may independentlyof one another be saturated or unsaturated, aliphatic or aromatichydrocarbon radicals which may also be linked to one another and may beidentical or different. For the purposes of this invention it is alsopossible for the carbon atom in (R^(˜)R^(˜˜)R^(˜˜˜)C)—Y^(˜) itself to beunsaturated. In that case said carbon atom is linked only to Y^(˜) andto one or two of the radicals R^(˜), R^(˜˜) or R^(˜˜˜). The radicalsR^(˜), R^(˜˜), and R^(˜˜˜) may independently of one another include anynumber of heteroatoms. The radicals R^(˜) R^(˜˜), and R^(˜˜˜) may be oflow molecular mass or may be polymeric in nature. Up to two of theradicals R^(˜), R^(˜˜), and R^(˜˜˜) may also be hydrogen atoms,moreover. At least one of the radicals R^(˜), R^(˜˜), and R^(˜˜˜) islinked by a chemical bond, to a polymer chain of kind A. The groupneeded for the coupling reaction is designated Y^(˜). In specificversions of this invention, single or plural radicals R^(˜), R^(˜˜), andR^(˜˜˜) may be of the same identity as R^(#), R^(##) or R^(###). It isalso in accordance with the invention if group X^(#) and group Y^(˜) areidentical. In this specific case the coupling takes place by means of acoupling reagent.

For the purposes of this invention it is possible to use an arbitrarilylarge number of further groups, which may enter into a bond with atleast one group X and/or at least one group Y.

A coupling reaction may proceed by formation of hydrogen bonds directlybetween the groups X^(#) and Y# so forming a species(R^(#)R^(##)R^(###)C)—X^(#)—Y^(˜)-(CR^(˜)R^(˜˜)R^(˜˜˜)) (see FIG. 2). Inspecific cases the coupling of groups X^(#) and Y^(˜) requires acoupling reagent X^(#a)—Y^(˜a) or X^(#a)—R^(a′)—Y^(˜a). X^(#a) andY^(˜a) are groups capable of forming hydrogen bridges with groups X^(#)and Y^(˜), respectively, and may be identical or different. It is alsopossible, furthermore, to link two groups X^(#) via coupling reagentY^(˜)—R^(b′)—Y^(˜) and also two groups Y^(˜) via a coupling reagentX^(˜) —R^(b′)—X^(˜). R^(a′) and R^(b′) can be saturated or unsaturated,aliphatic or aromatic hydrocarbon radicals and may contain an arbitrarynumber of heteroatoms. The radicals R^(a′) and R^(b′) may be of lowmolecular mass or may be polymeric in nature.

The coupleable groups may be unidentate or, preferably multidentate.Denticity refers in this case to the capacity of a group to form acertain number of hydrogen bonds. Hydrogen bonds between unidentate or,preferably, multidentate functional segments, as structure-formingelements, are known from a variety of examples. In nature, hydrogenbonds between complementary functional segments are used for theconstruction of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).A specific combination of donor and acceptor sites makes it possible forcouplings to be able to take place only in accordance with thelock-and-key principle. Where, for example, the functional segments α(“key” type) and β (“lock” type) are complementary segments which areable to form hydrogen bonds, then a compound is possible between α and βbut not between α and α or between β and β. With regard to the selectionof the functional segments, nature, when constructing DNA, restrictsitself to the two organic base pairs adenine/thymine (or uracil insteadof thymine in RNA) as bidentate segments and cytosine/guanine astridentate segments.

For the purposes of this invention it is possible to use polymers A andfiller particles B having groups based on adenine, thymine, uracil,cytosine, guanine, derivatives thereof, and also further compoundscapable of forming hydrogen bonds by the lock-and-key principle, suchas, for example, 2-ureido-4-pyrimidone and its derivatives,2,6-diacetylaminopyridine and its derivatives, diacetylpyrimidine andits derivatives, and ureidoacylpyrimidine and its derivatives. Thislisting makes no claim to completeness. Instead, the skilled worker isaware of further systems which can be used in accordance with theinvention. When this kind of functionalization is chosen, then, for thepurposes of this invention, either the at least one polymer kind Acarries groups of the “key” type and the at least one filler particle Bcarries groups of the “lock” type, or vice versa. FIG. 3 shows twoexamples of the coupling of reactive constituents via formation ofhydrogen bonds, by using two complementary groups; on the one hand, thedirect coupling of polymer A and filler particle B, and, on the other,the coupling of polymer A and filler particle B using a couplingreagent.

Likewise possible in accordance with the invention is the coupling ofgroups via coordinate bonds. Examples of coordinate bonds areligand-central atom bonds in complexes, i.e., the formation of acoordinate bond with metal atoms which may be present in elemental form,in the form of metal salts and/or in the form of metal complexes, andalso all other donor-acceptor bonds (in this regard see, for example, D.Philp, J. F. Stoddard, Angew. Chem., 1996, 108, 1242-1286; M. Rehahn,Acta Polym., 1998, 49, 201-224 or B. G. G. Lohmeijer, U.S. Schubert, J.Polym. Sci. A Polym. Chem., 2003, 41, 1413-1427).

If this coupling principle is chosen for the purposes of this invention,then the PSA comprises filler particles of kind B which contain groupshaving the general structure (R^(§)R^(§§)R^(§§§)C)—X^(§). R^(§), R^(§§)and R^(§§§) may independently of one another be saturated orunsaturated, aliphatic or aromatic hydrocarbon radicals which may alsobe linked to one another and may be identical or different. For thepurposes of this invention it is also possible for the carbon atom in(R^(§)R^(§§)R^(§§§)C)—X^(§) itself to be unsaturated. In that case saidcarbon atom is linked only to X^(§) and to one or two of the radicalsR^(§), R^(§§) or R^(§§§). The radicals R^(§), R^(§§), and R^(§§§) mayindependently of one another include any number of heteroatoms. Theradicals R^(§), R^(§§), and R^(§§§) may be of low molecular mass or maybe polymeric in nature. Up to two of the radicals R^(§), R^(§§), andR^(§§§) may also be hydrogen atoms, moreover. At least one of theradicals R^(§), R^(§§), and R^(§§§) is linked by a chemical or ionicbond, by chemisorption or physisorption, to a filler particle of kind B.The group needed for the coupling reaction is designated X^(§). At thesame time the PSA comprises polymers of kind A which contain groupshaving the general structure (R⁼R⁼⁼R⁼⁼⁼C)—Y⁼. R⁼, R⁼⁼ and R⁼⁼⁼ mayindependently of one another be saturated or unsaturated, aliphatic oraromatic hydrocarbon radicals which may also be linked to one anotherand may be identical or different. For the purposes of this invention itis also possible for the carbon atom in (R⁼R⁼⁼R⁼⁼⁼C)—Y⁼ itself to beunsaturated. In that case said carbon atom is linked only to Y⁼ and toone or two of the radicals R⁼, R⁼⁼ or R⁼⁼⁼. The radicals R⁼, R⁼⁼, andR⁼⁼⁼ may independently of one another include any number of heteroatoms.The radicals R⁼, R⁼⁼, and R⁼⁼⁼ may be of low molecular mass or may bepolymeric in nature. Up to two of the radicals R⁼, R⁼⁼, and R⁼⁼⁼ mayalso be hydrogen atoms, moreover. At least one of the radicals R⁼, R⁼⁼,and R⁼⁼⁼ is linked by a chemical bond, to a polymer chain of kind A. Thegroup needed for the coupling reaction is designated Y⁼. The groupsX^(§) and Y⁼ may be identical or different. If they are different, thenone of the varieties of groups takes on the donor function and the otherthe acceptor function that are necessary for the formation of coordinatebonds. If both groups are of the same kind, then the coordinate bond isformed by way of a coupling reagent.

The groups in the polymers A and filler particles B are advantageouslyconstructed such that they are capable of being able to form coordinatebonds with metals of type M, which may be in elemental form, in metalsalt form or in the form of metal complexes. Metal complexes may also bepolynuclear. Unidentate or multidentate segments may be employed. Thecoupling principle is depicted diagrammatically in FIG. 4. At least twogroups of the “key” type couple by coordination of M, which takes on the“lock” function. During the formation of the coordinate bond, thestructure of M may alter to become M′. This may be manifested in alteredoxidation states or else in an altered ligand structure and/or ligandcomposition. When using metal atoms it is particularly advantageous forthe purposes of this invention to take special precautions to disperse Min the PSA. This is preferably accomplished by choosing particularlysuitable counterions, in the case of metal salts, or particularlysuitable complex ligands, in the case of metal complexes. Suitablecounterions and complex ligands therefore take on the function ofcompatibilizers and dispersing assistants. It is particularlyadvantageous to disperse the metal atom M in a meltable matrix thatcontains no constituents able to enter into coordinate bonds with M.This mixture is metered into the rest of the PSA formulation, comprisingat least one polymer kind A and at least one filler particle kind B, notuntil immediately before the coating operation.

Particular preference is given to coupling using chelating segments.Examples of ligands which may be employed as groups are bipyridine andterpyridine and also their derivatives, acetylacetonate and itsderivatives, ethylenediaminetetraacetic acid and its derivatives,nitrilotriacetic acid and its derivatives,hydroxyethylethylenediaminetriacetic acid and its derivatives,diethylenetriaminepentaacetic acid and its derivatives, and carboxylicacids. This listing makes no claim to completeness. Instead, the skilledworker will be aware of further systems which may be used in accordancewith the invention. These groups are not reactive with one another. Allconstituents containing these groups can therefore be used in one massstream. The coupling of the groups takes place as soon as the mixturecomprising metal atom M is admixed to the mass stream, which for thepurposes of this invention takes place immediately prior to the coatingoperation.

Suitable metal atoms for the purposes of this invention are all thosechemical elements capable of acting as an acceptor for coordinate bonds.These are alkaline earth metals, preferably Ca and/or Mg, transitionmetals, preferably Ti, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Rh, Pd, W, Re,Os, Ir and/or Pt, and also Al and lanthanoids. Examples of suitablecompatibilizers and dispersing assistants for these metal atoms whichcan be used in accordance with the invention are alkoxides of aliphaticor aromatic, saturated or unsaturated molecules containing any desirednumber of heteroatoms, it being possible for these molecules to be oflow molecular mass or to be polymeric in nature. Additionally suitableare open-chain or cyclic unsaturated hydrocarbons which contain anynumber of heteroatoms and may be of low molecular mass or may bepolymeric in nature. Further dispersing assistants and compatibilizersfor M, useful in accordance with the invention, are low molecular masschelating compounds of organic identity.

Generally speaking, M can be an acceptor group (“key”) which inconjunction with a donor group of the “lock” type is able to form acoordinate bond. In this case the acceptor group may be attached topolymer A and filler particle B or else may be used in the form ofcoupling reagents. This general case is depicted diagrammatically inFIG. 5. It is further in accordance with the invention to use fillerparticles B and polymers A furnished with acceptor groups in combinationwith coupling reagents which carry donor groups.

For the purposes of this invention it is possible for any desiredcombinations of different sorts of coupling reactions to be employed. Inaccordance with the invention at least one kind of coupling reaction isused.

Methods of Producing Self-Adhesive Products

The production of self-adhesive products of the invention embraces theoperating steps of formulating/compounding, of coating, and ofcrosslinking.

Compounding Methods

The formulations of the invention can be produced using solvents insolvent kneading apparatus or else, for example, by using high-speeddispersers. Preferably, however, formulations of this kind are producedsolventlessly. Appropriate for this purpose are kneading apparatus, inbatch operation, and extruders, such as twin-screw extruders, incontinuous operation. Suitable compounding units for the purposes ofthis invention are those which contain dispersive and, optionally,distributive mixing elements. Dispersive mixing elements ensure veryfine distribution of the filler particles in the formulation, while thedistributive elements homogenize melted constituents such as resins orpolymers in the mixture of the PSA formulation. Particularly appropriatein solventless batch operation are Banbury mixers and also kneadingapparatus of Buss or Baker-Perkins type. In continuous operation,twin-screw extruders in corotating mode can be used with preference.

Coating Methods

Coating methods which can be employed for the purposes of this inventioninclude knife coating methods, nozzle knife coating methods, rolling rodnozzle methods, extrusion nozzle methods, casting nozzle methods, andcaster methods. Likewise in accordance with the invention areapplication methods such as roll application methods, printing methods,screen-printing methods, patterned roll methods, ink-jet methods, andspraying methods. For the feeding of the coating unit of the inventionit is possible as an option to include a conveying and/or mixingassembly, e.g., a single-screw or twin-screw extruder, between meteringsystem and mixing system. The extruder which can be used alternativelyis separately heatable.

Crosslinking Methods

It is particularly preferred to initiate the crosslinking of the PSAfollowing the operation of applying it by coating. Particularlyadvantageous for this purpose is a radiation process. One very preferredvariant that may be mentioned, and that be used for the purposes of thisinvention, is that of crosslinking with ultraviolet radiation. By meansof brief exposure to light in a wavelength range between 200 to 400 nm,the coated material, which in this version of the invention contains thephotoinitiator functions preferably as groups X and/or groups Y, isirradiated and hence crosslinked. Employed in particular for thispurpose are high-pressure or medium-pressure mercury lamps at a power of80 to 240 W/cm. Other radiation sources which can be used for thepurposes of this invention are those familiar to the skilled worker.Alternatively, the emission spectrum of the lamp is adapted to thephotoinitiator used, or the type of photoinitiator is adapted to thelamp's spectrum. The intensity of irradiation is adapted to therespective quantum yield of the UV photoinitiator, to the degree ofcrosslinking that is to be set, and to the web speed.

Furthermore, it is possible with preference to crosslink the PSAformulations of the invention with electron beams after they have beenapplied by coating. This may also take place in combination with a UVcrosslinking operation. Typical irradiation equipment that may beemployed includes linear cathode systems, scanner systems, and segmentedcathode systems where electron beam accelerators are concerned. Typicalacceleration voltages are situated in the range between 50 kV and 1 MV,preferably between 80 kV and 300 kV. The radiation doses employed aresituated between 5 to 250 kGy, in particular between 20 and 100 kGy.

For the purposes of this invention it is additionally possible withpreference to realize the crosslinking by exposure to thermal energy.This can be done optionally in combination with one or more radiationmethods. Where thermal energy is used to initiate the crosslinkingreaction, care must be taken to ensure that, during the coatingoperation, the crosslinking process has not progressed too far, sincethis alters the coating characteristics of the formulation. Particularpreference is given in this case to producing a compound which alreadycomprises filler particles of kind B and polymers of kind A, but withthe groups X and Y selected such that they are able to react notdirectly with one another but rather only through the intermediacy of acrosslinker or a coupling reagent. In that case, crosslinkers orcoupling reagents are preferably metered into the otherwise fullyhomogenized compound immediately prior to the coating operation, and aremixed with said compound. With particular preference a two-component ormulticomponent operation is conducted in which all of the raw materialshave been divided up between at least two mass reservoirs in such a wayas to ensure the physical separation, up until immediately prior to thecoating operation, of all those raw materials that are capable of athermal reaction with one another. The thermal energy is then eithertaken from the preheated mass streams, made available by setting atemperature of the coating unit, or realized by way of a heating tunneland/or an infrared section after the coating operation. It is likewisepossible in accordance with the invention to utilize the thermal energygiven off in one or more exothermic reactions in order for this thermalreaction to proceed. Combinations of these methodological possibilitiesparticularly with the radiation crosslinking methods are possible withinthe context of this invention.

With great preference in the context of this invention, self-adhesiveproducts of the invention are produced in a continuous operation in thecourse of which the steps of compounding, of coating, and ofcrosslinking are coupled directly and hence in which an inline operationis employed.

Self-Adhesive Products Product Constructions

The pressure-sensitive adhesives prepared by the processes of theinvention can be utilized for constructing different kinds ofself-adhesive products such as, for example, self-adhesive tapes orself-adhesive sheets. Inventive constructions of self-adhesive productsare depicted in FIG. 6. Each layer in the self-adhesive tapeconstructions of the invention may, as an alternative, be in foamedform.

In the simplest case a self-adhesive product of the invention iscomposed of the pressure-sensitive adhesive (PSA) in single-layerconstruction (construction in FIG. 6.1). This construction mayoptionally be lined on one or both sides with a release liner, e.g., arelease film or release paper. The layer thickness of the PSA istypically between 1 μm and 2000 μm, preferably between 5 μm and 1000 μm.

The PSA may additionally be on a backing, in particular a film or paperbacking or a sheetlike textile structure (construction in FIG. 6.2). Thebacking in this case may have been pretreated in accordance with theprior art on the side facing the PSA, so that, for example, animprovement in PSA anchorage is obtained. The side may also have beenprovided with a functional layer which can act, for example, as abarrier layer. The reverse of the backing may have been pretreated inaccordance with the prior art so as to achieve, for example, a releaseeffect. The reverse of the backing may also have been printed. The PSAmay optionally be lined with a release paper or release film. The PSAhas a typical layer thickness of between 1 μm and 2000 μm, preferablybetween 5 μm and 1000 μm.

In the case of the construction according to FIG. 6.3 the self-adhesiveproduct is a double-sided product comprising as its middle layer, forexample, a backing film, a backing paper, a sheetlike textile structureor a backing foam. In this construction, PSAs of the invention ofidentical or different kind and/or of identical or different layerthickness are employed as top and bottom layers. The backing (orcarrier) may in this case have been pretreated in accordance with theprior art on one or both sides, thereby achieving, for example, animprovement in PSA anchorage. It is also possible for one or both sidesto have been provided with a functional layer which connect, forexample, as a barrier layer. The PSA layers may optionally be lined withrelease papers or release films. The layers of PSA typically havethicknesses, independently of one another, of between 1 μm and 2000 μm,preferably between 5 μm and 1000 μm.

As a further double-sided self-adhesive product, the constructionaccording to FIG. 6.4 is an inventive variant. A PSA layer of theinvention carries on one side a further PSA layer which, however, may beof any desired nature and therefore need not be inventive. Theconstruction of this self-adhesive product may be lined optionally withone or two release films or release papers. The layers of PSA typicallyhave thicknesses, independently of one another, of typically between 1μm and 2000 μm, preferably between 5 μm and 1000 μm.

As in the case of the construction in FIG. 6.4, the constructionaccording to FIG. 6.5 is a double-sided self-adhesive product whichcomprises a PSA of the invention and also one other PSA of any kind. InFIG. 6.5, however, two PSA layers are separated from one another by abacking (or carrier), a backing film, backing paper, a sheetlike textilestructure or a backing foam. The backing in this case may have beenpretreated in accordance with the prior art on one or both sides,thereby achieving, for example, an improvement in PSA anchorage. It isalso possible for one or both sides to have been provided with afunctional layer which connect, for example, as a barrier layer. The PSAlayers may optionally be lined with release paper or release film. ThePSA layers have thicknesses, independently of one another, of typicallybetween 1 μm and 2000 μm, preferably between 5 μm and 1000 μm.

The self-adhesive product of the invention according to FIG. 6.6comprises a layer of inventive material as a middle layer, which isprovided on both sides with any desired PSAs of identical or differenttype. One or both sides of the middle layer may have been provided witha functional layer which connect, for example, as a barrier layer. Forthe outer PSA layers it is not necessary for inventive PSAs to beemployed. The outer PSA layers may optionally be lined with releasepaper or release film. The outer PSA layers have thicknesses,independently of one another, of typically between 1 μm and 2000 μm,preferably between 5 μm and 1000 μm. The thickness of the middle layeris typically between 1 μm and 2000 μm, preferably between 5 μm and 1000μm.

Test Methods

In the description of this invention, numerical values are given forsystems of the invention and reference is made to test methods by meansof which such data can be determined. These test methods are collatedbelow.

Determination of Processing Properties (Test A)

Melt viscosities (Test A1) and first normal stress differences aredetermined for solvent-free, uncrosslinked test specimens as a functionof shear rate and temperature by means of a PC-controlled high-pressurecapillary rheometer from Göttfert (model: Rheograph 2002) from thepressure drops measured in the steady-state flow range. The capillaryused is, for example, a flat slot with geometry of 23 mm×25 mm×0.16 mm(L×W×H). Values for the shear rates, viscosities, and first normalstress differences indicate that in this description are corrected data.The shear rate chosen for the tests is 1000 s⁻¹. The measurementtemperature depends on the nature of the material under investigationand is reported together with the results. From the data for shear rate,viscosity, and first normal stress difference, the R value is determinedas a ratio between the first normal stress difference and the product ofviscosity and shear rate (Test A2).

Determining the Gel Fraction (Test B)

Coated and crosslinked, solvent-free PSA samples are welded into anonwoven polyethylene pouch. Soluble constituents are extracted withtoluene for a period of three days, the solvent being replaced daily.The difference in sample weights before and after extraction gives thegel index, as the percentage weight fraction of the polymer which cannotbe extracted with toluene.

Determining the Bond Strength (Test C)

The peel strength (bond strength) is tested in accordance with PSTC-1. APSA layer 50 μm thick is applied to a PET film 25 μm thick. A strip ofthis specimen 2 cm wide is adhered to a sanded steel plate by rollingover the specimen back and forth five times using a 5 kg roller. Theplate is clamped in and the self-adhesive strip is pulled off from itsfree end on a tensile testing machine at a peel angle of 180° and aspeed of 300 mm/min.

Determining the Holding Power (Test D)

The test takes place in accordance with PSTC-7. A PSA layer 50 μm thickis applied to a PET film 25 μm thick. A strip of this specimen 1.3 cmwide is adhered to a polished steel plaque over a length of 2 cm using a2 kg roller, the specimen being rolled over back and forth twice. Theplaques are equilibrated under test conditions (temperature andatmospheric humidity) for 30 minutes, but without a load. Then the testweight is hung on, thereby producing a shearing stress parallel to thesurface of the bond, and a measurement is made of the time taken for thebond to fail.

TABLE 1 Functional groups of type Y   Functional groups of type X    —CR^(a)═CR^(b)R^(c)     —OC(═O)CR^(d)═CR^(a)R^(b)    —OCR^(a)═CR^(b)R^(c)

—CR¹═CR²R³ X X X —OC(═O)CR⁴═CR¹R² X X X —OCR¹═CR²R³ X X X

X —NCO X —NR¹R² X X —N₃ X X X —OH X —SH X X —C(═O)R¹ —C(═O)—OH X—C(═O)—O—C(═O)R¹ Cyclic acid anhydride —PI X X X X —C≡CR¹ —CR⁵R⁶H X X XFunctional groups of type Y Functional groups of type X   —NCO  —NR^(a)R^(b)   —N₃   —OH   —SH   —C(═O)R^(a)   —C(═O)—OH —CR¹═CR²R³ X X—OC(═O)CR⁴═CR¹R² X X —OCR¹═CR²R³ X

X X X X X —NCO X X X X X —NR¹R² X X X —N₃ —OH X X —SH X X —C(═O)R¹ X—C(═O)—OH X X X —C(═O)—O—C(═O)R¹ X X X X Cyclic acid anhydride X X X X—PI —C≡CR¹ X —CR⁵R⁶H Functional groups of type Y   Functional groups oftype X     —C(═O)—O—C(═O)R^(a) Cyclic acid anhydride     —PI    —C≡CR^(a)     —CR^(e)R^(f)H   —CR¹═CR²R³     X   X —OC(═O)CR⁴═CR¹R² X X—OCR¹═CR²R³ X X

X —NCO —NR¹R² X X —N₃ X —OH X X —SH X X —C(═O)R¹ —C(═O)—OH X X—C(═O)—O—C(═O)R¹ Cyclic acid anhydride —PI X X —C≡CR¹ X —CR⁵R⁶H X

1. A process for preparing a pressure-sensitive adhesive comprisingcrosslinking at least one polymer having functional groups Y, saidpolymer being admixed with at least one kind of functionalizedparticles, said polymers having at least one nonpolymeric base unit witha surface modification of the base unit, the surface modification of theparticles having at least one kind of functional groups X, wherein thecrosslinking is initiated by exposure to radiation energy or thermalenergy, and the crosslinking of the polymer results in a reaction of thefunctional groups X of the particles and the functional groups Y of thepolymer.
 2. The process as claimed in claim 1, wherein the at least onebase unit of the at least one functionalized kind of particle is aninorganic amorphous or crystalline oxide.
 3. The process as claimed inclaim 1, wherein the at least one base unit of the at least onefunctionalized kind of particle is an alkaline earth metal salt.
 4. Theprocess as claimed in claim 1, wherein the at least one base unit of theat least one functionalized kind of particle is a silicate-basedmineral.
 5. The process as claimed in claim 1, wherein the functionalgroups Y of the at least one polymer and/or the functional groups X ofthe at least one kind of particle have an at least partlyphotoinitiating character.
 6. The process as claimed in claim 1, whereinthe surface modification of the at least one functionalized kind ofparticle is brought about by means of organosilanes, surfactants,organotitanium compounds, fatty acids and/or polyelectrolytes.
 7. Theprocess as claimed in claim 1, wherein the reaction for bringing aboutthe crosslinking of the pressure-sensitive adhesive is a couplingreaction, particularly one involving the formation of covalent bondshydrogen bonds and/or coordinative bonds.
 8. The process as claimed inclaim 1, wherein the crosslinking reaction is initiated substantially byradiation.
 9. The process as claimed in claim 1, wherein the at leastone functionalized kind of particle is present in the form of singularspherical particles, singular platelet-shaped particles and/or singularrodlet-shaped particles.
 10. The process as claimed in claim 1, whereinthe at least one functionalized kind of particle is present in the formof particle aggregates formed from a plurality of primary particles. 11.The process as claimed in claim 9, wherein the particles have a spatialextent of not more than 1000 nm.
 12. The process as claimed in claim 1,wherein the weight fraction of functionalized particles in thepressure-sensitive adhesive is up to 50%.
 13. A pressure-sensitiveadhesive comprising at least one crosslinked polymer component, thecrosslinking of the polymer component being brought about at least inpart by incorporation of functionalized particles, the particles havingat least one nonpolymeric base unit and also a surface modification ofthis base unit, and the surface modification of the particles having atleast one kind of functional groups X which are capable of reacting withfunctional groups Y present in the polymer component.
 14. (canceled) 15.A cross-linking reagent comprising surface-modified functionalizedparticles having a nonpolymeric base unit.
 16. A self-adhesive productcomprising the pressure-sensitive adhesive of claim
 13. 17. The processof claim 2, wherein said particle is a metal oxide or a semimetal oxide.18. The process of claim 4, wherein said silicate-based mineral is aclay mineral.
 19. The process of claim 8, wherein said radiation is UVradiation.
 20. The process as claimed in claim 10, wherein the particleaggregates have a spatial extent of not more than 1000 nm.
 21. Theprocess as claimed in claim 20, wherein the particle aggregates have aspatial extent in at least one spatial direction of not more than 250nm.
 22. The process as claimed in claim 21, wherein the particleaggregates have a spatial extent in at least one spatial direction ofnot more than 100 nm.
 23. The process as claimed in claim 11, whereinthe particles have a spatial extent in at least one spatial direction ofnot more than 250 nm.
 24. The process as claimed in claim 23, whereinthe particles have a spatial extent in at least one spatial direction ofnot more than 100 nm.
 25. The process of claim 12, wherein said weightfraction of functionalized particles is up to 20%.
 26. The process ofclaim 21, wherein said weight fraction of functionalized particles is upto 12%.